He that doeth sin (o poiwn thn amartian). "He that keeps on doing sin" (the habit of sin). Of the devil (ek tou diabolou). In spiritual parentage as Jesus said of the Pharisees in John 8:44 . When one acts like the devil he shows that he is not a true child of God. Sinneth from the beginning (ap arch amartanei). Linear progressive present active indicative, "he has been sinning from the beginning" of his career as the devil. This is his normal life and those who imitate him become his spiritual children. That he might destroy (ina lush). Purpose clause with ina and the first aorist active subjunctive of luw. This purpose (ei touto) Jesus had and has. There is eternal conflict, with final victory over Satan certain.